Effects of gamma radiation on Shewanella putrefaciens CN-32's reduction of iron in ferrihydrite, goethite, lepidocrocite and alginate co-precipitates

Gamma radiation is regularly used to sterilize sediments in experiments as it causes very little mineralogical transformations, especially in comparison to sterilization at high temperature with autoclaving. However, some recent studies have suggested that gamma radiation can induce the reduction of ferric iron during the sterilization process. The project tests whether gamma-radiation induces Fe(III) reduction in synthetic iron oxides, representative of natural biogenic iron oxides. Various doses of gamma radiation are applied to 3 different iron oxides (i.e., ferrihydrite, goethite, and lepidocrocite) with and without organic material (i.e., alginate). Rate of microbial Shewanella putrefaciens CN-32 reduction of gammaand non-gamma radiated iron oxides are determined with Ferrozine Assay in order to assess the effect of radiation. The results of this project will help determine whether gamma radiation sterilization should continue to be used for sterilization of iron oxides sediments and if investments in other methods of sterilization should be made. Project Background